Astronomy Explained Upon Sir Isaac Newton's Principles / And made easy to those who have not studied mathematics

by James Ferguson

INDEX.

The numeral Figures refer to the Articles, and the small n to the Notes on the Articles.

• A.
• Acceleration of the Stars, [221].
• Angle, what, [185].
• Annual Parallax of the Stars, [196].
• Anomaly, what, [239].
• Antients, their superstitious notions of Eclipses, [329].
  • Their method of dividing the Zodiac, [398].
• Antipodes, what, [122].
• Apsides, line of, [238].
• Archimedes, his ideal Problem for moving the Earth, [159].
• Areas described by the Planets, equal in times, [153].
• Astronomy, the great advantages arising from it both in our religious and civil concerns, [1] Discovers the laws by which the Planets move, and are retained in their Orbits, [2]
• Atmosphere, the higher the thinner, [174].
  • It’s prodigious expansion, ib.
  • It’s whole weight on the Earth, [175].
  • Generally thought to be heaviest when it is lightest, [176].
  • Without it the Heavens would appear dark in the day-time, [177].
  • Is the cause of twilight, ib.
  • It’s height, ib.
  • Refracts the Sun’s rays, [178].
  • Causeth the Sun and Moon to appear above the Horizon when they are really below it, ib.
  • Foggy, deceives us in the bulk and distance of objects, [185].
• Attraction, [101-105].
  • Decreases as the square of the distance increases, [106].
  • Greater in the larger than in the smaller Planets, [158].
  • Greater in the Sun than in all the Planets if put together, ib.
• Axes of the Planets, what, [19].
  • Their different positions with respect to one another, [120].
• Axis of the Earth, it’s parallelism, [302].
  • It’s position variable as seen from the Sun or Moon, [338].
    • the Phenomena thence arising, [340].
• B.
• Bodies, on the Earth, lose of their weight the nearer they are to the Equator, [117].
  • How they might lose all their weight, [118],
  • How they become visible, [167].
• C.
• Calculator, (an Instrument) described, [436].
• Calendar, how to inscribe the Golden Numbers rightly in it for shewing the days of New Moons, [423].
• Cannon-Ball, it’s swiftness, [89].
  • In what times it would fly from the Sun to the different Planets and fixed Stars, ib.
• Cassini, his account of a double Star eclipsed by the Moon, [58].
  • His Diagrams of the Paths of the Planets, [138].
• Catalogue of the Eclipses, [327].
  • Of the Constellations and Stars, [367].
  • Of remarkable Æras and events, [433].
• Celestial Globe improved, [438].
• Centripetal and centrifugal forces, how they alternately overcome each other in the motions of the Planets, [152-154].
• Changes in the Heavens, [403].
• Chords, line of, how to make, [369].
• Circles, of perpetual Apparition and Occultation, [128].
  • Of the Sphere, [198].
  • Contain 360 Degrees whether they be great or small, [207].
• Civil Year, what, [411].
• Columbus (Christopher) his story concerning an Eclipse, [330].
• Clocks and Watches, an easy method of knowing whether they go true or false, [223].
  • Why they seldom agree with the Sun if they go true, [228-245].
  • How to regulate them by Equation Tables and a Meridian line, [225], [226].
• Cloudy Stars, [402].
• Cometarium (an Instrument) described, [437].
• Constellations, antient, their number, [396].
  • The number of Stars in each, according to different Astronomers, [399].
• Cycle, Solar, Lunar, and Romish, [420].
  • Of Easter, [425].
• D.
• Darkness at our Saviour’s crucifixion supernatural, [352], [432].
• Day, natural and artificial, what, [417].
  • And Night, always equally long at the Equator, [126].
  • Natural, not compleated in an absolute turn of the Earth on it’s Axis, [222].
• Degree, what, [207].
• Digit, what, [321], n.
• Direction, (Number of) [426].
• Distances of the Planets from the Sun, an idea thereof, [89].
  • A Table thereof, [98].
  • How found, [190].
• Diurnal and annual Motions of the Earth illustrated, [200], [202].
• Dominical Letter, [427].
• Double projectile force, a balance to a Quadruple Power of Gravity, [153].
  • Star covered by the Moon, [58].
• E.
• Earth, it’s bulk but a point as seen from the Sun, [3] It’s Diameter, annual Period, and Distance from the Sun, [47].
  • Turns round it’s Axis, ib.
  • Velocity of it’s equatoreal Parts, ib.
  • Velocity in it’s annual Orbit, ib.
  • Inclination of it’s Axis, [48].
  • Proof of it’s being globular, or nearly so, [49], [314].
  • Measurement of it’s surface, [50], [51].
  • Difference between it’s Equatoreal and Polar Diameters, [76].
  • It’s motion round the Sun demonstrated by gravity, [108], [111].
    • by Dr. Bradley’s observations, [113].
    • by the Eclipses of Jupiter’s Satellites, [219].
  • It’s diurnal motion highly probable from the absurdity that must follow upon supposing it not to move, [111]. [120].
    • and demonstrable from it’s figure, [116].
    • this motion cannot be felt, [119].
  • Objections against it’s motion answered, [112], [121].
  • It has no such thing as an upper or under side, [122].
    • in what case it might, [123].
  • The swiftness of it’s motion in it’s Orbit compared with the velocity of light, [197].
  • It’s diurnal and annual motions illustrated by an easy experiment, [200].
  • Proved to be less than the Sun and bigger than the Moon, [315].
• Easter Cycle, [425].
• Eclipsareon (an Instrument) described, [442].
• Eclipses, of Jupiter’s Satellites, how the Longitude is found by them, [207-218].
  • • they demonstrate the velocity of light, [216].
  • Of the Sun and Moon, [312-327].
  • Why they happen not in every month, [316].
  • When they must be, [317].
  • Their limits, ib.
  • Their Period, [320], [326].
  • A dissertation on their progress, [321-324].
  • A large catalogue of them, [327].
  • Historical ones, [328].
  • More of the Sun than of the Moon, and why, [331].
  • The proper Elements for their calculation and projection, [353-390].
• Ecliptic, it’s Signs, their names and characters, [91].
  • Makes different Angles with the Horizon every hour and minute, [275].
    • how these Angles may be estimated by the position of the Moon’s horns, [260].
  • It’s obliquity to the Equator less now than it was formerly, [405].
  • How it’s Signs are numbered, [354].
• Elongations, of the Planets, as seen by an observer at rest on the outside of all their Orbits, [133].
  • Of Mercury and Venus as seen from the Earth, illustrated, [142].
    • it’s quantity, [143].
  • Of Mercury, Venus, the Earth, Mars, and Jupiter; it’s quantity as seen from Saturn, [147].
• Epochas or Æras, [433].
• Equation of time, [224-245].
  • Of the Moon’s Place, [355].
  • Of the Sun’s Place, ib.
  • Of the Nodes, [363].
• Equator, day and night always equal there, [126].
  • Makes always the same Angle with the Horizon of the same place; the Ecliptic not, [274], [275].
• Equinoctial Points in the Heavens, their precession, [246],
  • a very different thing from the recession or anticipation of the Equinoxes on Earth, the one no ways occasioned by the other, [249].
• Excentricities of the Planets Orbits, [155].
• F.
• Fallacies in judging of the bulk of objects by their apparent distance, [185];
  • applied to the solution of the horizontal Moon, [187].
• First Meridian, what, [207].
• Fixed Stars, why they appear of less magnitude when viewed through a telescope than by the bare eye, [391].
  • Their number, [392].
  • Their division into different Classes and Constellations, [395-399].
• G.
• General Phenomena of a superior Planet as seen from an inferior, [149].
• Gravity, demonstrable, [101-104].
  • Keeps all bodies on the Earth to it’s surface, or brings them back when thrown upward; and constitutes their weight, [101], [122].
  • Retains all the Planets in their Orbits, [103].
  • Decreases as the square of the distance increases, [106].
  • Proves the Earth’s annual motion, [108].
  • Demonstrated to be greater in the larger Planets than in the smaller; and stronger in the Sun than in all the Planets together, [158].
  • Hard to understand what it is, [160].
  • Acts every moment, [162].
• Globe, improved celestial, [438].
• Great Year, [251].
• H.
• Harmony of the celestial motions, [111].
• Harvest-Moon, [273-293].
  • None at the Equator, [273].
  • Remarkable at the Polar Circles, [285].
  • In what years most and least advantageous, [292].
• Heat, decreases as the square of the distance from the Sun increases, [169].
  • Why not greatest when the Earth is nearest the Sun, [205].
  • Why greater about three o’Clock in the afternoon than when the Sun is on the Meridian, [300].
• Heavens, seem to turn round with different velocities as seen from the different Planets; and on different Axes as seen from most of them, [120].
  • Only one Hemisphere of them seen at once from any one Planet’s surface, [125].
  • The Sun’s Center the only point from which their true Motions could be seen, [135].
  • Changes in them, [403].
• Horizon, what, [125], n.
• Horizontal-Moon explained, [187].
• Horizontal Parallax, of the Moon, [190];
  • of the Sun, [191];
  • best observed at the Equator, [193].
• Hour-Circles, what, [208].
• Hour of time equal to 15 degrees of motion, ib.
  • How divided by the Jews, Chaldeans, and Arabians, [419].
• Huygenius, his thoughts concerning the distance of some Stars, [5]
• I. J.
• Inclination of Venus’s Axis, [29].
  • Of the Earth’s, [48].
  • Of the Axis or Orbit of a Planet only relative, [201].
• Inhabitants of the Earth (or any other Planet) stand on opposite sides with their feet toward one another, yet each thinks himself on the upper side, [122].
• Julian Period, [430].
• Jupiter, it’s distance, diameter, diurnal and annual revolutions, [67-69].
  • The Phenomena of it’s Belts, [70].
  • Has no difference of seasons, [71].
  • Has four Moons, [72],
    • their grand Period, [73],
    • the Angles which their Orbits subtend as seen from the Earth, [74],
    • most of them are eclipsed in every revolution, [75].
  • The great difference between it’s equatoreal and polar Diameters, [76].
  • The inclination of it’s Orbit, and place of it’s Ascending Node, [77].
  • The Sun’s light 3000 times as strong on it as Full Moon-light is on the Earth, [85].
  • Is probably inhabited, [86].
  • The amazing strength required to put it in motion, [158].
  • The figures of the Paths described by it’s Satellites, [269].
• L.
• Light, the inconceivable smallness of it’s particles, [165],
  • • and the dreadful mischief they would do if they were larger, [166].
  • It’s surprising velocity, [166],
    • compared with the swiftness of the Earth’s annual motion, [197].
  • Decreases as the square of the distance from the luminous body increases, [169].
  • Is refracted in passing through different Mediums, [171-173].
  • Affords a proof of the Earth’s annual motion, [197], [219].
  • In what time it comes from the Sun to the Earth, [216],
    • this explained by a figure, [217].
• Limits of Eclipses, [317].
• Line, of the Nodes, what, [317];
  • • has a retrograde motion, [319].
  • Of Sines and Chords, how to make, [369].
• Long (Rev. Dr.) his method of comparing the quantity of the surface of dry land with that of the Sea, [51].
  • His glass sphere, [126].
• Longitude, how found, [207-213].
• Lucid Spots in the Heavens, [401].
• Lunar Cycle deficient, [422].
• M.
• Magellanic Clouds, [402].
• Man, of a middle size, how much pressed by the weight of the Atmosphere, [175];
  • why this pressure is not felt, ib.
• Mars, it’s Diameter, Period, Distance, and other Phenomena, [64-67].
• Matter, it’s properties, [99].
• Mean Anomaly, what, [239].
• Mercury, it’s Diameter, Period, Distance, &c. [22].
  • Appears in all the shapes of the Moon, [23].
  • When it will be seen on the Sun, [24].
  • The inclination of it’s Orbit and Place of it’s Ascending Node, ib.
  • It’s Path delineated, [138].
  • Experiment to shew it’s Phases and apparent Motion, [142].
• Mercury (Quicksilver) in the Barometer, why not affected by the Moon’s raising Tides in the Air, [311].
• Meridian, first, [207].
  • Line, how to draw one, [226].
• Milky Way, what, [400].
• Months, Jewish, Arabian, Egyptian, and Grecian, [415].
• Moon, her Diameter and Period, [52].
  • Her phases, [53], [255].
  • Shines not by her own light, [54].
  • Has no difference of seasons, [55].
  • The Earth is a Moon to her, [56].
  • Has no Atmosphere of any visible Density, [58];
    • nor Seas, [59].
  • How her inhabitants may be supposed to measure their year, [62].
  • Her light compared with day-light, [85].
  • The excentricity of her Orbit, [98].
  • Is nearer the Earth now than she was formerly, [163].
  • Appears bigger in the Horizon than at any considerable height above it, and why, [187];
    • yet is seen much under the same Angle in both cases, [188].
  • Her surface mountainous, [252]:
    • if smooth she could give us no light, ib.
  • Why no hills appear round her edge, [253].
  • Has no Twilight, [254].
  • Appears not always quite round when full, [256].
  • Her phases agreeably represented by a globular Stone viewed in Sun-shine when she is above the Horizon, and the observer placed as if he saw her on the top of the Stone, [258].
  • Turns round her Axis, [262].
  • The length of her Solar and Sidereal Day, ib.
  • Her periodical and synodical revolution represented by the motions of the hour and minute hands of a Watch, [264].
  • Her Path delineated, and shewn to be always concave to the Sun, [265-268].
  • Her motion alternately retarded and accelerated, [267].
  • Her gravity toward the Sun greater than toward the Earth at her Conjunction, and why she does not then abandon the Earth on that account, [268].
  • Rises nearer the time of Sun-set when about the full in harvest for a whole week than when she is about the full at any other time of the year, and why, [273-284]:
    • this rising goes through a course of increasing and
    • decreasing benefit to the farmers every 19 years, [292].
  • Continues above the Horizon of the Poles for fourteen of our natural Days together, [293].
  • Proved to be globular, [314].
    • and to be less than the Earth, [315].
  • Her Nodes, [317].
    • ascending and descending, [318].
    • their retrograde motion, [319].
  • Her acceleration proved from antient Eclipses, [322], n.
  • Her Apogee and Perigee, [336].
  • Not invisible when she is totally eclipsed, and why, [346].
  • How to calculate her Conjunctions, Oppositions, and Eclipses, [355-390].
  • How to find her age in any Lunation by the Golden Number, [423].
• Morning and Evening Star, what, [145].
• Motion, naturally rectilineal, [100].
  • Apparent, of the Planets as seen by a spectator at rest on the outside of all their Orbits, [133];
    • and of the Heavens as seen from any Planet, [154].
• N.
• Natural Day, not compleated in the time that the Earth turns round it’s Axis, [222].
• New and Full Moon, to calculate the times of [355].
• New Stars, [403],
  • cannot be Comets, [404].
• New Style, it’s original, [414].
• Nicias’s Eclipse, [328].
• Nodes, of the Planet’s Orbits, their places in the Ecliptic, [20].
  • Of the Moon’s Orbit, [317].
    • their retrograde motion, [319].
• Nonagesimal Degree, what, [259].
• Number of Direction, [426].
• O.
• Objects, we often mistake their bulk by mistaking their distance, [185].
  • Appear bigger when seen through a fog than through clear Air, and why, ib.
    • this applied to the solution of the Horizontal Moon, [187].
• Oblique Sphere, what, [131].
• Olympiads, what, [323]. n.
• Orbits of the Planets not solid, [21].
• Orrery described, [434], [435], [436].
• P.
• Parallax, Horizontal, what, [190].
• Parallel Sphere, what, [131].
• Path of the Moon, [265], [266], [267].
  • Of Jupiter’s Moons, [269].
• Pendulums, their vibrating slower at the Equator than near the Poles proves that the Earth turns on it’s Axis, [117].
• Penumbra, what, [336].
  • It’s velocity on the Earth in Solar Eclipses, [337].
• Period of Eclipses, [320], [326].
• Phases of the Moon, [252-268].
• Planets, much of the same nature with the Earth, [11].
  • Some have Moons belonging to them, [12].
  • Move all the same way as seen from the Sun, but not as seen from one another, [18].
  • Their Moons denote them to be inhabited, [86].
  • The proportional breadth of the Sun’s Disc as seen from each of them, [87].
  • Their proportional bulks as seen from the Sun, [88].
  • An idea of their distances from the Sun, [89].
  • Appear bigger and less by turns, and why, [90].
  • Are kept in their Orbits by the power of gravity, [101], [150-158].
  • Their motions very irregular as seen from the Earth, [137].
  • The apparent motions of Mercury and Venus delineated by Pencils in an Orrery, [138].
  • Elongations of all the rest as seen from Saturn, [147].
  • Describe equal areas in equal times, [153].
  • The excentricities of their Orbits, [155].
  • In what times they would fall to the Sun by the power of gravity, [157].
  • Disturb one another’s motions, the consequence thereof, [163].
  • Appear dimmer when seen through telescopes than by the bare eye, the reason of this, [170].
• Planetary Globe described, [439].
• Polar Circles, [198].
• Poles, of the Planets, what, [19].
  • Of the world, what, [122].
  • Celestial, seem to keep on the same points of the Heavens all the year, and why, [196].
• Projectile Force, [150];
  • if doubled would require a quadruple power of gravity to retain the Planets in their Orbits, [153].
  • Is evidently an impulse from the hand of the Almighty, [161].
• Precession of the Equinoxes, [246-251].
• Ptolemean System absurd, [96], [140].
• R.
• Rays of Light, if not disturbed, move in straight lines, and hinder not one another’s motions, [168].
  • Are refracted in passing through different mediums, [171].
• Reflection of the Atmosphere causes the Twilight, [177].
• Refraction of the Atmosphere bends the rays of light from straight lines, and keeps the Sun and Moon longer in sight than they would otherwise be, [178].
  • A surprising instance of this, [183].
  • Must be allowed for in taking the Altitudes of the celestial bodies, ib.
• Right Sphere, [131].
• S.
• Satellites; the times of their revolutions round their primary Planets, [52], [73], [80].
  • Their Orbits compared with each other, with the Orbits of the primary Planets, and with the Sun’s circumference, [271].
  • What sort of Curves they describe, [272].
• Saturn, with his Ring and Moon’s, their Phenomena, [78], [79], [82].
  • The Sun’s light 1000 times as strong to him as the light of the Full Moon is to us, [85].
  • The Phenomena of his Ring farther explained, [204].
• Our blessed Saviour, the darkness at his crucifixion supernatural, [352].
  • The prophetic year of his crucifixion found to agree with an astronomical calculation, [432].
• Seasons, different, illustrated by an easy experiment, [200];
  • • by a figure, [202].
• Shadow, what, [312].
• Sidereal Time, what, [221];
  • • the number of Sidereal Days in a year exceeds the number of Solar Days by one, and why, [222].
  • An easy method for regulating Clocks and Watches by it, [223].
• Signs of the Zodiac, their names and characters, [91], [365].
  • How they are numbered by Astronomers, [354].
• Sines, line of, how to make, [369].
• Smith, (Rev. Dr.) his companion between Moon-light and Day-light, [85].
  • His demonstration that light decreases as the square of the distance from the luminous body increases, [169].
  • (Mr. George) his Dissertation on the Progress of a Solar Eclipse, [321-324].
• Solar Astronomer, the judgment he might be supposed to make concerning the Planets and Stars, [135], [136].
• Sphere, parallel, oblique, and right, [131].
  • It’s Circles, [198].
• Spring and Neap Tides, [302].
• Stars, their vast distance from the Earth, [3], [196].
  • Probably not all at the same distance, [4] Shine by their own light, and are therefore Suns [7],
    • probably to other worlds, [8] A demonstration that they do not move round the Earth, [111].
  • Have an apparent slow motion round the Poles of the Ecliptic, and why, [251].
  • A catalogue of them, [399].
  • Cloudy, [402].
  • New, [403].
  • Some of them change their places, [404].
• Starry Heavens have the same appearance from any part of the Solar System, [132].
• Sun appears bigger than the Stars, and why, [4] Turns round his Axis, [18].
  • His proportional breadth as seen from the different Planets, [87].
  • Describes unequal arcs above and below the Horizon at different times, and why, [130].
  • His Center the only place from which the true motions of the Planets could be seen, [135].
  • Is for half a year together visible at each Pole in it’s turn, and as long in visible, [200], [294].
  • Is nearer the Earth in Winter than in Summer, [205].
  • Why his motion agrees so seldom with the motion of a well regulated Clock, [224-245].
  • Would more than fill the Moon’s Orbit, [271].
  • Proved to be much bigger than the Earth, and the Earth to be bigger than the Moon, [315].
  • To calculate his true place, [360].
• Systems, the Solar, [17-95];
  • the Ptolemean, [96];
  • the Tychonic, [97].
• T.
• Table, of the Periods, Revolutions, Magnitudes, Distances, &c. of the Planets, facing § [99].
  • Of the Air’s rarity, compression, and expansion at different heights, [174].
  • Of refractions, [182].
  • For converting time into motion, and the reverse, [220].
  • For shewing how much of the celestial Equator passes over the Meridian in any part of a mean Solar Day; and how much the Stars accelerate upon the mean Solar time for a month, [221].
  • Of the first part of the Equation of time, [229];
    • of the second part, [241].
  • Of the precession of the Equinox, [247].
  • Of the length of Sidereal, Julian, and Tropical Years, [251].
  • Of the Sun’s place and Anomaly, following [251].
  • Of the Equation of natural Days, following [251]
  • Of the Conjunctions of the hour and minute hands of a Watch, [264].
  • Of the Curves described by the Satellites, [272].
  • Of the difference of time in the Moon’s rising and setting on the parallel of
    • London every day during her course round the Ecliptic, [277].
  • Of Eclipses, [327].
  • For calculating New and Full Moons and Eclipses, following [390].
  • Of the Constellations and number of the Stars, [399].
  • Of the Jewish, Egyptian, Arabic, and Grecian months, [415].
  • For inserting the Golden Numbers right in the Calendar, [423].
  • Of the times of all the New Moons for 76 years, [424].
  • Of remarkable Æras or Events, [433].
  • Of the Golden Number, Number of Direction, Dominical Letter and Days of the Months, following [433].
• Thales’s Eclipse, [323].
• Thucydides’s Eclipse [324].
• Tides, their Cause and Phenomena, [295-311].
• Tide-Dial described, [441].
• Trajectorium Lunare described, [440].
• Tropics, [198].
• Twilight, none in the Moon, [254].
• Tychonic System absurd, [97].
• U.
• Universe, the Work of Almighty Power, [5], [161].
• Up and down, only relative terms, [122].
• Upper or under side of the Earth no such thing, [123].
• V.
• Velocity of Light compared with the velocity of the Earth in it’s annual Orbit, [197].
• Venus, her bulk, distance, period, length of days and nights, [26].
  • Shines not by her own light, ib.
  • Is our morning and evening Star, [28].
  • Her Axis, how situated, [29].
  • Her surprising Phenomena, [29-43].
  • The inclination of her Orbit, [45].
  • When she will be seen on the Sun, ib.
  • How it may probably be soon known if she has a Satellite, [46].
  • Appears in all the Shapes of the Moon, [23], [141].
  • An experiment to shew her phases and apparent motion, [141].
• Vision, how caused, [167].
• W.
• Weather, not hottest when the Sun is nearest to us, and why, [205].
• Weight, the cause of it, [122].
• World not eternal, [164].
• Y.
• Year, [407],
  • Great, [251],
  • Tropical, [408],
  • Sidereal, [400],
  • Lunar, [410],
  • Civil, [411],
  • Bissextile, ib.
  • Roman, [413],
  • Jewish, Egyptian, Arabic, and Grecian, [415],
  • how long it would be if the Sun moved round the Earth, [111].
• Z.
• Zodiac, what, [397].
  • How divided by the antients, [398].
• Zones, what, [199].